1. Technical Field
The present invention relates to liquid ejecting heads and liquid ejecting apparatuses. The liquid ejecting head and the liquid ejecting apparatus according to the invention have piezoelectric elements, with which they can eject droplets through nozzle openings they have. Each piezoelectric element has a piezoelectric layer and electrodes formed on this piezoelectric layer. The piezoelectric layer is made of a piezoelectric material.
2. Related Art
A typical form of piezoelectric element is composed of a piezoelectric material having an electromechanical conversion function (e.g., a piezoelectric layer composed of crystals of dielectric materials) and two electrodes sandwiching it. This form of piezoelectric element is used in liquid ejecting heads or similar kinds of devices, serving as flexural-vibration-based actuators. A typical example of liquid ejecting heads is ink jet recording heads. An ink jet recording head has nozzle openings for ejecting ink droplets, and these nozzle openings individually communicate with pressure chambers. These pressure chambers share a diaphragm as one of their components. Piezoelectric elements vibrate to deform some portions of the diaphragm, and then the deformed portions of the diaphragm pressurize appropriate ones of the pressure chambers. As a result, the ink contained in these pressure chambers is ejected in the form of droplets from appropriate ones nozzle openings. A typical method for fabricating piezoelectric elements for this type of liquid ejecting head is as follows: A diaphragm is completely coated with a uniform layer of a piezoelectric material by any kind of film formation method, and then the obtained layer is lithographically cut into smaller pieces fitting pressure chambers.
As in JP-A-2001-223404, lead zirconate titanate (PZT) is often used as a piezoelectric material to fabricate this type of piezoelectric element.
Recently, however, environment-conscious people have called for low-lead piezoelectric materials. An example of lead-free piezoelectric materials is bismuth ferrite (BiFeO3), crystals of which form the perovskite structure (general formula: ABO3). BiFeO3-based piezoelectric materials can be crystallized at a relatively low temperature owing to their high Curie point and high degree of spontaneous polarization, but they are problematic in other ways; their poor insulation performance often leads to a large amount of leakage current. Note that these problems are not unique to ink jet recording heads and other kinds of liquid ejecting heads; similar problems may be encountered with the fabrication of piezoelectric elements that are used as actuators in other kinds of apparatuses.